Lock decoder and decoding method

ABSTRACT

A decoder and method for decoding certain lever tumbler locks. The locks include a case having an inner surface, a bolt with a fence, a cylinder with a keyway, and a column of lever tumblers, each having a gate. It is essential that the spacings between said inner surface and the near edge thereto of each tumbler, when the tumbler gates are aligned with the fence, be known and identical. It is also essential that the possible depth settings of the tumblers be known. The method involves determining by trial and error the key bit heights which will pivot said near edge of each tumbler flush against said inner surface and calculating the actual depth setting of each tumbler by subtracting said spacing between said ibner surface and said near tumbler edge from said determined key bit heights. The decoder includes a pair of interchangeable gage keys each of which has a bit with a height equal to the sum of one of the possible depth settings and said spacing between the inner surface and said near tumbler edge, means for adjusting the depth of said bit in the keyway to the plane of each tumbler and a trio of shims which are inserted into the keyway behind the bit to increase the bit height to heights equal to the sum of another one of the possible depth settings and said spacing between said inner surface and said near tumbler edge.

llnited States Patent '91 Lee [54] LOCK DECODER AND DECODING METHOD [76] Inventor: David G. Lee, 2136 N. Orange Street, Stockton, Calif. 95204 [22] Filed: July 6, 1971 [21 Appl.l lo.:159,827

[56] References Cited UNITED STATES PATENTS 5/1957 Harwell ..33/l74F 3/1935 Hansen ..ss/174r Primary Examiner-Francis S. l-lusar Attorney-Boyken, Mohler, Foster & Schwab [57] ABSTRACT A decoder and method fordecoding certain lever tumbler locks. 'The locks include a case having an any 29,1973

inner surface, a bolt with a fence, a cylinder with a keyway, and a column of lever tumblers, each having a gate. It is essential that the spacings between said inner surface and the near edge thereto of each tumbler, when the tumbler gates are aligned with the fence, be known and identical. lt is also essential that the possible depth settings of the tumblers be known. The method involves determining by trial and error the key bit heights which will pivot said near edge of each tumbler flush against said inner surface and calculating the actual depth setting of each tumbler by subtracting said spacing between said ibner surface and said near tumbler edge from said determined key bit heights. The decoder includes a pair of interchangeable gage keys each of which has a bit with a height equal to the sum of one of the possible depth settings and said spacing between the inner surface and said near tumbler edge, means for adjusting the depth of said bit in the keyway to the plane of each tumbler and a trio of shims which are inserted into the keyway behind the bit to increase the bit height to heights equal to the sum of another one of the possible depth settings and said spacing between said inner surface and said near tumbler edge.

6 Claims, 22 Drawing Figures PATENIE M29 I973 SHEET 1 OF 6 Mh-M I 5M ATTORNEYS PATENTELHHZQISH 3 735 A96 SHEET 2 UF 6 INVENTOR.

BY DAV/D 6. L515 13W, MME

ATTMNEVS A 'm-mzmms 1 3,735,496

7 SHEET30F6 44 IENTOR. L DA VII) 5. LEE F I lEr BY .7- W %ZM PATENI ED Mm 91913 TUMBLERS SHEET 4 BF 6 TURN/N6 AXIS 2 5 3i- 4 BE -E 5 e 55 7 43d 8 43 9 g Q J, g as S? GAGE KEY KEV FIG. 12C FIGIIZB BYDAV/D T fEZ BW,M,M5M

ATTORNEYS I LUCK IDIECGDIEII AND DECGDWG GI BACKGROUND OF INVENTION This invention relates to a decoder and method for decoding certain lever tumbler locks.

Lever tumbler locks have a series of flat lever tumblers positioned opposite the keyway of the lock cylinder. They are unlocked by pivoting the gates of the tumblers into alignment opposite the fence or post of the bolt with a key, thereby permitting the bolt to be retracted. Lever tumbler locks which are used in safes and safe deposit boxes are usually of standard construction. Key variation, and thus security, is achieved by using change tumblers whose gates may be positioned at different distances from the mrning axis of the key. Each setting requires a different key height to move the tumbler into alignment with the fence. In the art this is expressed as the depth setting" of the tumbler and as used herein that term means the distance between the turning axis of the key and the point on the key bearing surface of the tumbler nearest to the key when the gate is aligned opposite the fence.

Certain commerical makes-of lever tumbler locks contain nine lever tumblers, eight of which are change tumblers each having seven difierent depth settings. Each depth setting difiers from the next by the same increment. For convenience depth settings are numerically coded by assigning an, integer to each setting, with low integers'representing the greater depth settings, as follows:

Numerical Code Depth setting (in.)'

The code" for such a lock is a nine digit number (one for each tumbler), each digit representing the depth setting of a tumbler beginning with the first tumbler from the top of the keyway.

, By knowing the depth setting of each tumbler and its position in the series of tumblers, (the code of the lock) a key may be cut which will open the lock. However, for security reasons written records of lock codes are not usually kept or, if they are, they are often lost or misplaced. Also, these locks are normally mounted so that the keyway is the only ready access to the tumblers. Consequently, if the existing keys are misplaced or lost, and the code is not known, the lock must be decoded or forcibly entered by drilling, tapping, flame cutting or punching. I-Ieretofore there has been no reliable method for decoding such lever tumbler locks.

The decoder and method of this invention are based on the fact thatin certain commercial lever tumbler locks the distances between the inner surface of one side of the lock case and the nearest edges of the tumblers to that side when the tumbler gates are aligied with the fence, are identical. In the commercial locks having the above listed depth settings, this distance is 0.120 in. By knowing this distance and determining the key height which will pivot said nearest edge of each tumbler flush against that inner surface, the depth setting of each tumbler may be calculated.

DESCION OF INVENTION In brief, the method of this invention involves mechanically determining by trial and error the key height which will pivot each said nearest edge flush against said inner surface and calculating the depth setting by subtracting from the determined key heights the predetermined distance between said nearest edge and said inner surface when the tumbler gates are aligied. Specifically, this mechanical determination may be made by; (a) determining the maximum degree the keyway will turn without initiating retraction of the bolt; (b) inserting a key having a height equal to the sum of the smallest possible depth setting and said predetermined distance into the lock keyway at each tumbler position, (c) sequentially increasing said height by the known increment between depth settings, and (d) turning the key at each height in the sequence until a height is reached at which the keyway will not make its maximum degree of rotation.

The decoder for carrying out the method of this invention'includes; (a) a gage key for inserting in the keyway, having a bit of height equal to the sum of the smallest possible depth setting and said predetermined distance, (b) means for adjusting the depth of the bit in the keyway to the plane of each tumbler and temporarily fixing the bit at each such depth, and (c) means forsequentially increasing the height of the bit by the known increment between depth settings.

Accordingly, one of the objects of this invention is to provide a decoder for decoding certain lever tumbler locks without forcibly entering the lock.

Another object of this invention is to provide a decoder which uses the lock keyway as the sole access to the tumblers.

A further object is to provide a decoder which is simple to operate and quickly and efliciently decodes certain lever tumbler locks.

An additional object is to provide a method for solv ing a lockout from a compartment which is locked with a certain lever tumbler lock.

A still further object is to provide a method for replacing a lost key for a certain lever tumbler lock when the code thereof is unknown.

FIG. I is a perspective side view of a preferred form of the decoder of this invention and a lever tumbler lock installed within a door of a safe or other secured enclosure.

FIG. 2 is a perspective side view of the key which fits the lever tumbler lock of FIG. I.

FIG. 3 is a partial top plan view of the lock of FIG. I with the lock cover plate removed.

FIG. 41 is an exploded perspective view of the decoder of FIG. ll.

FIG. 5 is a perspective view of one of the gage keys of the decoder of FIG. 1.

FIG. 6 is an enlarged side elevational view of the decoder of FIG. I.

FIG. 7 is an enlarged side elevational view of the gage key of FIG. 5.

FIG. 8 is a plan sectional view line 3-8 of FIG. 6. I

FIG. 9 is a plan sectional view of the decoder taken along line 99 of FIG. 6.

FIG. 10 is a plan sectional view of the decoder taken along line l0-l of FIG. 6.

FIG. II is a plan sectional view of the decoder taken along line ill-ll of FIG. 6.

of the decoder along FIGS. 12A, 12B and 12C are, respectively, diagram-' matic representations of (a) various positions of the lever tumblers during the practice of the method of this invention; (b) the gage key bit heights which are required to pivot the tumbler flush against the inner surface of the lock case and (c) a key which would unlock a lock having the illustrated tumbler depth settings.

FIGS. 13A, 13B, 13C and 13D are a sequence of fragmentary plan views of the lock of FIG. 1 with one of the gage keys (in cross section) inserted in the keyway, illustrating steps of the decoding method.

FIGS. 14A, 14B, 14C and 14D are a sequence of fragmentary plan vews of the lock of FIG. 1 with a second gage key (in cross section) inserted on the keyway, illustrating additional decoding steps.

Similar reference characters refer to like parts throughout the several views of the drawings.

DESCRIPTION OF A PREFERRED EMBODIMENT Description of the Lock FIGS. 1, 2 and 3 illustrate a lever tumbler lock and key therefor. The construction and dimensions of commercial makes of such locks are well known. Therefore, only a partial description of the basic portions of this type of lock will be given.

As seen in FIG. 3, the front of the lock is at the bottom and the rear of the lock is at the top. The lock includes a hollow rectangular case or housing 1 which is mounted within a door or other body 2 (FIG. 1) in a secured enclosure with its front 3 flush with the door jamb. The bolt 4 of the lock is slidably received through an opening an opening in the front 3. The bolt has a fence or post 5 extending from its inner edge toward the back side of the case. A cylinder 6 is supported within the case between the top and bottom sides thereof for partial rotation and has a keyway 7 extending radially through it from its top to its bottom. The cylinder also has a cam means (not shown) attached to its bottom which engages the rear of the bolt 4 and causes retraction of the bolt when the proper key is inserted in the keyway and turned clockwise.

A column of flat lever tumblers 8 (FIG. 1) is pivotally supported in the case about pin 9. In the particular locks to which this invention is directed there are usually nine tumblers in the column, each equidistantly spaced by a thin, flat spacer (not shown). Each tumbler in the column is held against a stop 10 by a flat spring 14 (FIG. 3). Each tumbler has a gate 15 notched in its front edge. The gates receive the fence 5 of the bolt when it is retracted.,lf all the tumbler gates are not aligned directly opposite the fence 5, the bolt cannot be retracted. Each tumbler also has a key bearing surface 16 which opposes the cylinder. When a proper key (FIG. 2) is inserted in the keyway and turned, the bits 21 of the key engage the key bearing surfaces 16 at the front edges thereof and slide rearwardly along them pivoting the tumblers away from the turning axis of the key. As a bit 21 reaches the arcuate portion 22 (FIG. 3) of a key bearing surface 16, the tumbler ceases pivoting and the cam means on the bottom of the cylinder 6 is actuated. The bolt is retracted as the key bit turns clockwise along the arcuate portion 22.

0f the nine tumblers the bottommost (not shown) is usually a so called trap tumbler." It is a single piece tumbler having a known depth setting. The other eight tumblers are so called change tumblers. As shown in FIG. 3 each change tumbler, generally designated 17,

consists of a lower portion 18 and an upper portion 19. The gate 15 is notched into the front edge of the lower portion; whereas the key bearing surface 16 is formed in the upper portion. Each portion 18 and 19 has a set of equidistantly spaced teeth 24, 25, respectively, which may be enmeshed at seven different positions, thereby providing seven difierent depth settings, each differing from the next by an identical amount. The possible depth settings of such a change tumbler may be represented by the formula wherein A is the shortest depth setting, B is the distance each setting differs from the next and n is an integer in the range of 0 to 6, inclusive. Since these locks are of standard known construction, the magnitudes of A and B are known or may be easily measured. Such a lock is decoded by determining A n8 for each tumbler.

In order for the lock to be susceptible to decoding according to this invention the spacing between the edge 26 of each tumbler and the inner surface 27 of the lock case, when the tumbler gates 15 are aligned opposite the fence 5, must be substantially identical and of known magnitude. This spacing may be easily measured in an unmounted lock.

FIG. 2 illustrates a key which is used to open the above described lock. The key has nine cuts 20 (one for each tumbler) of slightly greater width than the thickness of the tumblers. The cuts are made such that they lie in the respective planes of the tumblers when the key is fully inserted in the keyway. Each cut leaves a bit 21 having a height equal to the depth setting of the tumbler in the corresponding position for engaging the key bearing surface of that tumbler.

Description of the Decoder The decoder is shown in FIGS. 1 and 4 through 11, and as seen therein the top of the decoder is on the left, the bottom is on the right, the front is at the bottom and the rear is at the top. a

As shown in FIGS. 4 and 5, the principal parts of the decoder are: an elongated body 29, a pair of interchangeable gage keys 30, 31 (numbered 3 and 6, respectively), an elongated slide stop 32 and a set of three shims 33, 34, 35. The gage keys (one at a time), stop and shims are all slidably and removably attached to the body. Body 29 has a pair of T-shaped channels or slots 39, 40 in its opposed elongated sides 41, 42 extending the full lengths thereof. Slot 40 receives stop 32 and gage keys 30, 31 below stop 32; whereas slot 39 receives shims 33, 34, 35 one below the other in that order.

As illustrated in FIGS. 5, 6, and 7 gage keys 30, 31 are identical except that the bit 43 of gage key 30 is larger than the bit 44 of gage key 31. Each gage key includes a flat, rectangular notched bow 45 for sliding rearwardly into slot 40, an elongated stem 46 extending from the forward, bottom comer of the bow, and a bit (43, 44) located near the forward end of the stem. Stem 46 is joined to the bow comer by a short neck 47 which tends the lower edge of the stem slightly below and parallel to the bottom edge of the bow and into vertical alignment with bottom side of body 29. When the bow is slid into 40 the rear edge of the neck 47 acts as a stop. Each bow 45 has eight equidistantly spaced notches 48 formed in its top edge. The spacing between those notches is the same as the spacing between the lever tumblers in the lock keyway 7. There are numbers on the bow directly under the notches which relate to the positions of the eight change tumblers in the lock. Thus, the number 2 notch corresponds to the second change tumbler (from the top of the keyway) and so forth.

A flat gage key dog 49 is pivotally supported in a slot 50 in body 29 about a pin 51. Slot 50 is aligned directly above the arm of T-shaped slot 40 so that dog 49 is aligned directly above the bow of the gage key which is within slot 40. Dog 49 has a tooth-like appendage 52 extending from its forward, bottom edge for engaging the notches 48 in the bow of the gage key. A small helical spring 53 positioned in the rear of slot 50 exerts an upward force on the portion of the dog behind pin 51 thus pivoting appendage 52 into snug engagement with the notches 48. The distance between the ends of stems 46 and the bits 43, 44 is such that when either gage key 30, 31 is inserted to the bottom of the keyway 7 and the appendage 52 is engaged in notch number 8, the bits 43, 44 will lie in the plane of the eighth change tumbler of the lock. Correlatively, the distance between the forward end of the stem 46 and the bits 43, 44 when either gage key 30, 31 is inserted to the bottom of the keyway and the appendage 52 is engaged in notch number 8, is equivalent to the distance between the bottom of the lock keyway and the plane of the eighth change tumbler.

The height of bit 43 (h in FIG. 6) as measured from the bottom edge of the stem 46 to the top end of the bit 43 is equal to the distance:

A+3E+the spacing between tumbler edge 26 and lock case inner surface 27 when the tumbler gates are aligned with the fence, wherein A and B are as previously defined. The height of bit 44, similarly measured, is equal to the distance:

A the spacing between tumbler edge 26 and lock case inner surface 27 when the tumbler gates are aligned with the fence, wherein A and B as previously defined.

The slide stop 32 (FIGS. 1, 4 and 9) is the means by which the depth of a gage key in the keyway is adjusted and referenced so that when the appendage 52 is engaged in a given notch 48 the gage key bit will lie in the plane of the corresponding tumbler. Slide stop 32 comprises a generally rectangular body section 55 having a T-shaped projection 56 sized to fit and slide into slot 40. A set screw 57 extends through a threaded bore 54 in body section 55 for temporarily fixing the position of the slide stop in slot 40. An elongated member 58 extends forwardly from the bottom front corner of body section 55 adjacent the side of decoder body 29. The forward end of member 58 has a shoulder 65 extending from its inner edge, which fits snugly against the bottom front corner of decoder body 29 and acts as a stop to prevent the slide stop from being slid out the rear of slot 40. The front end 59 of member 58 is flat and blunt for fitting snugly against the top of the lock cylinder 6 (See FIG 12).

The shims 33, 34, 35 (FIGS. 4, 6-11) are the means by which the bit height is sequentially increased. Each shim has a head 61 (FIG. 4) wiht a T-shaped projection 66 sized for fitting and sliding into slot 39 in decoder body 29. A spring backed ball bearing 67 is mounted in the inner side of each T-shaped projection 66 to prevent the shims from sliding in slot 39 due to their own weight. A flat flag shaped member 62 is attached to the bottom of each head and extends therefrom below the bottom of the decoder body 29. The flat pole portion 66 of each member 62 extends forwardly from the bottom front corner of the flag portion of member 62 through an aperture 63 in a thin shoulder 69 which extends downwardly fi'om the front bottom edge of decoder body 29.

The heads 61 of the shims 33, M, 33 line up one behind the other in slot 39 and the pole portions 63 are aligned adjacent and parallel one below the other. The lengths of the pole portions 63 are such that when the shims 33, 34, 35 are slid to their forwardmost positions in slot 39 each pole portion will extend the same distance forwardly from the front end of body 29. Thus the pole portion of shim 33 is longer than the pole portion of shim 34 by an amount equal to the width of the flag portion of shim 34. Likewise the pole portion of shim 34 is longer than the pole portion of shim 35 by an amount equal to the width of the flag portion of shim 35.

The pole portion of each shim 33, 35 is the same width as the stem 46 of each gage key. Each pole portion has a thickness equal to B as defined above. As shim 35 is slid forwardly in slot 39 its pole portion slides under and adjacent to the bottom of stem 46 of the gage key for the full length thereof, thus increasing the height of the bit of the gage key by B. Likewise as shim 34 is slid forwardly in slot 39 the pole portion thereof slides under and adjacent to the bottom of the pole portion of shim 35; thus, again increasing the bit height by B. Shim 33 may be similarly slid forwardly in slot 39 to increase the bit height by B a third time.

A small screw 71 (FIG. 4) received in threaded bore 72 acts as a stop to prevent the shims 33, 34, 35 from being slid out the rear of slot 39.

Decoding the lock The manipulation of decoder is directed toward determining the gage key bit heights which will pivot the edges 26 of the tumblers flush against the inner surface 27 of the lock case. The depth setting of each tumbler may then be calculated by subtracting the predetermined distance between the edges 26 and the inner lock case surface 27 when the tumbler gages are aligned opposite the bolt fence from said gage key bit heights.

The first step in the method is to determine the maximum degree of rotation of the lock cylinder without initiating unlocking retraction of the bolt. The cyinders of the above described locks normally rotate freely for about before the bolt cam means (previously discussed) engages the bolt. Accordingly, this maximum degee of rotation may be found by inserting the tip of a key or a small screw driver in the keyway, turning the keyway counter-clockwise as far as possible (this farthest counter-clockwise position is hereinafter referred to as the starting position), placing a small mark at a point on the periphery of the top of the cylinder, tuming the cylinder clockwise as far as possible and making a small mark on the lock case or door surface opposite the mark on the periphery of the cylinder. in FIGS. 1, 13, and 14, these marks are represented by small arrowheads.

The next step is to reference the settings of appendage 32 in notches to the corresponding change tumbler positions. This is accomplished by first placing appendage 32 into the number 6 notch of gage key 36.

The slide stop set screw 57 is then loosened and the stem 46 of gage key 30 is inserted into the keyway 7. The dec2der is tilted forward and the pole portions of shims 38,34,35 are slid behind stem 46 into the keyway. (The decoder should always be tilted forward in the keyway before inserting a shim). The decoder is then moved to an upright position and pushed to the bottom of the keyway. Thj slide stop 32 is slid down agalnst the top of The cylindr 6. Finally, the set screw 57 is tightened, being careful that the shims are held flat against the inner edge of the keyway 7.

In order to remove the stem 46 of either gage key 30, 31 from the keyway all the shims 33, 34, 35 must first be retracted from the keyway. This follows throughout the decoding procedure.

After the above described adjustment, the decoder is in condition for carrying out the decoding step. FIGS. 12 through 14 illustrate this procedure which basically involves:

l. at each tumbler position sequentially increasing the gage key bit height by B with the shims 33, 34, 35 and 2. turning the gage key in the keyway at each bit height in the sequence until a bit height is reached at which the cylinder 6 will not rotate to its maximum degree (as described above) because the edge 26 of the tumbler has been pivoted against the inner surface 27 of the lock case. Since the change tumblers of the lock may be set at any one of 7 depth settings ranging from A to A 68, this procedure theoretically requires using a sequence of at least 8 bit heights each differing by B. However, in practice it is not necessary to test at a bit height equal to A plus said spacing between edge 26 and inner surface 27 because at that bit height the cylinder will always rotate its maximum degree. Also, if the cylinder makes its maximum rotation at a bit height of A 68 said spacing between edge 26 and inner surface 27 (the highest possible in the sequence) it is not necessary to test at A 7B said spacing between edges 26 and inner surface 27 since at thelatter bit height the cylinder will never rotate its maximum. Theoretically this procedure could be carried out using a decoder having a single gage key with a bit height of A B said spacing between edges 26 and surface 27 and five shims each of thickness B, rather than the above-described decoder which uses two interchangeable gage keys and three shims. However, it is practical to use the latter in order to enable testing at all seven depth settings. Also, the stem 46 must be rigid and strong enough to withstand the shear forces put on it when it is turned in the keyway. With normal construction materials the stem must be of such size that it would be impossible to get it and more than three shims into the keyway. This problem is circumvented by using the two interchangeable gage keys 30, 31 both of which have a rigid, strong stem which, when backed by three shims, will fit into the keyway.

It may also be possible to begin the testing at the highest possible bit height and sequentially decrease the bit height by B (for instance, by retracting shims) until a height is reached at which the cylinder will rotate its maximum. However, it has been found more convenient to carry out the decoding procedure starting with smaller bit heights and increasing it as described above.

For convenience the same numerical code is used for the various bit heights as is used for the depth settings.

Thus the number 6 gage key without any shims backing it, hasl bit height equal to;

A said spacing between edge 26 and inner surface 27 Since the numerical designation of the gage key decreases by l with each increase of B a shim represents 1 in this code. Thus the number 6 gage key backed by two shims is effectively a number 4 gage key and so forth.

FIGS. 13A-D and FIGS. 14A-D the testing sequence being made at a given tumbler position using the decoder of FIG. 1. It is advantageous to start with the first tumbler and work downward or vice versa. The four illustrations of FIG. 13 show the seem 36 of the number 3 gage key in cross section with from zero to three shims (also in cross section) inserted in the lock keyway and turned as far as possible clockwise. In FIG. 13A the gage key number 3 with no shims has turned the cylinder its maximum degree of rotation indicated by the alignment of the arrowhead marks on the cylinder periphery and lock case. (A bit height at which the cylinder rotates its maximum is termed a G0; whereas a bit height at which the cylinder cannot be rotated its maximum is termed a NO-GO) This means that a higher bit height is required to get a NO-GO. Since the number 3 gage key without any shims was a G0, the decoder is turned back to the starting posifion, tilted slightly forward and the shim 35 is inserted into the keyway.

As shown in FIG. 13B the number 3 gage key with one shim (in effect a number 2 gage key) was also a G0. Similarly, the number 3 gage key with two shims (FIG. 13C) was a G0. However, as shown in FIG. 13, the number 3 gage key with three shims (in eflect a number 0 gage key) was a NO-GO." The NO-GO condition is brought about because the edge 26 has been pivoted against the inner surface 27 thus preventing the cylinder from turning its maximum, indicated by the nonalignment of the arrowhead marks on the cylinder top and lock case. The NO-GO condition establishes the immediately preceding GO bit height of FIG. 13C as the bit height at which the bit will pivot edge 26 flush against inner surface 27.

If the number 3 gage key with three shims had been a GO" this would automatically establish it as the setting which pivots edge 26 against inner surface 27 because it is the highest possible bit height.

Ifthe number 3 gage key without any shims is a N0- GO," this means either the number 4, 5 or 6 gage key may be the one which pivots edge 26 flush against inner surface 27. In that instance the decoder is withdrawn from the lock, the number 3 gage key is withdrawn from the decoder and the number 6 gage key is inserted in its place. This occurrence is shown in FIG. 14A and the subsequent testing with the number 6 gage key and shims is shown in FIGS. 14B, C and D. The latter three illustrations show the stem 46 of number 6 gage key in cross section with from zero to three shims (also in cross section) inserted in the lock keyway and turned as far as possible clockwise. As indicated in FIGS. 14B and C, the tests with the number 6 gage key and number 5 gage key were GO; whereas the test with the number 4 gage key was NO-GO. This indicates that the number 5 gage key has the bit height which pivots edge 26 flush against inner surface 27.

When the bit height which pivots edge 26 flush against inner surface 27 has been determined for a given tumbler, the depth setting of that tumbler may be are aligned with the fence from said determined bit height. However, inasmuch as the numerical code of the gage key bit heights corresponds to the numerical code of the depth settings, i.e., a number 1 gage key corresponds to a number 1 depth setting and so forth, this calculation is made automatically by such correspondence.

FIGS. 12A-C illustrate the relationship between a set of hypothetical lock tumbler depth settings, corresponding gage key bit heights and a key for such a lock. Referring to the illustration of the tumblers, the arrows at the left (top) of the illustration represent the distances the tumblers must be pivoted to move their edges 26 flush against the inner surface 27'. The set of arrows at the right indicate the distance the gate of each tumbler must be pivoted to align with the fence. The sum of this second distance and the distance between the turning axis and stop line is equal to the depth setting. The vertical alignment indicates the position of the edges 26 of each tumbler when the gates are aligned with the fence. As shown this line is parallel to the inner surface of the case wall; thus the distance between each edge 26 and the inner surface, when the gates are aligned, is identical.

The gage key bit height illustration shows the bit heights required to pivot edge 26 of each tumbler flush against the inner surface 27. These heights are equivalent to the sum of the lengths of the arrows at the left of the tumbler illustration and the distance between the stop and tuming axis lines.

The key shown in the third illustration will open the lock since its bits will pivot each tumbler gate into alignment with the fence. The bit heights of the key are equal to the depth settings of the tumblers. Each key bit height differs from its corresponding gage key bit height by the distance between the vertical alignment line and the inner surface 27.

The code of the key shown in FIG. 12C is 165326403. A key having this code may be cut by established key making procedures. Such procedures normally involve placing the blank key together with a so-called space key (which positions the cuts properly) and a so-called depth key (which establishes the depth of the cut) in a vice and making the custs with an appropriate cutting tool.

Other modifications and ramifications of the lock decoder and decoding method described above will be apparent to those skilled in the locksmith and mechanical arts. It is intended that such modifications and ramifications be included within the scope of this invention as defined by the following claims.

I claim:

1. A method'for decoding a lever tumbler lock including a case having an inner surface, a bolt having a fence, said bolt being slidably received in said case, a cylinder having a keyway, a column of lever tumblers pivotally supported within said case about a fixed axis intermediate said cylinder and said inner surface, each tumbler having a gate formed therein, the spacings between said inner surface and the near edge thereto of mined and equidistantly spaced, said method comprisa. determining by trial and error the key bit height which will pivot said near edge of each tumbler flush against said inner surface by inserting keys each having a single bit into the keyway at each tumbler position and turning said keys therein, the bit of each key being of difierent height equal to the sum of said spacing between said inner surface I and the near edge thereto of the tumbler and one of the possible depth settings; and

b. calculating the depth setting for each tumbler by subtracting said spacing between said inner surface and the near edge thereto of the tumbler from the key bit height determined in (a).

2. A method for decoding a lever tumbler lock including a case having an inner surface, a bolt slidably each tumbler when said tumbler gates are aligned with 6 said fence being predetermined and equal and the possible depth settings of said tumblers being predeterreceived in said case, said bolt having a fence, a cylinder including a keyway and a bolt retracting means and being supported within said case for partial rotation about a fixed axis, a column of lever tumblers pivotally supported within said case about a second fixed axis intermediate said cylinder and said inner surface, each tumbler having a gate formed therein, the spacings between said inner surface and the near edge thereto of each tumbler when the gates of the tumblers are aligned with the fence being predetermined and equal, and the possible depth settings of said tumblers being:

wherein A is known and is the shortest possible depth setting, n is O or a positive integer and B is a predetermined, constant distance, said method comprising:

a. deten'nining the maximum degree of rotation of said cylinder without actuating said bolt retracting means to retract said bolt;

b. inserting a gage key having a bit with a height equal to A said spacing between said inner surface and the near edge thereto of each tumbler when the gates of the tumblers are aligned with the fence into said key way at each tumbler position;

c. at each tumbler position sequentially increasing the height of said bit by B and turning said gage key in the keyway to engage the tumbler at such positionfor pivoting thereof at each height in the sequence until a height is reached at which said cylinder will not make said maximum degree of rotation because said near edge of the tumbler has been pivoted against said inner surface, thereby establishing the immediately preceding bit height in the sequence as the bit height at which the bit pivots said near edge of the tumbler flush against said inner surface; and

d. calculating A n8 for each tumbler by subtracting from said immediately preceding bit height said spacing between said inner surface and the near edge thereto of each tumbler when the gages of the tumblers are aligned with the fence.

3. The method according to claim 2 in which:

e. A is approximately 0.140 inch;

f. n is an integer in the range of 0 and 6, inclusive; and

g. B is approximately 0.040 inch.

4. A decoder for decoding a lever tumbler lock, said lock including a case having an inner surface, a bolt slidably received in said case, said bolt having a fence, a cylinder including a keyway, and being supported within said case for partial rotation about a fixed axis, a column of lever tumblers pivotally supported within said case about a second fixed axis intermediate said cylinder and said inner surface, each tumbler having a gate formed therein, the spacing between said inner surface and the near edge thereto of each tumbler when the gates of the tumblers are aligned with the fence being predetermined and equal, and the possible depth settings of said tumblers being:

wherein A is known and is the shortest possible depth setting, n is an integer in the range of and 6 inclusive and B is a predetermined, constant distance, said decoder comprising:

a. a body having a first slot and a second slot;

b. a pair of interchangeable gage keys slidably and removably received in said first slot for inserting one at a time in said keyway, each of said gage keys including an elongated stem and a bit extending from said stem, the bit of one of said gage keys havinga height equal to A said spacing between said inner surface and said near edge of said tumbler when the tumbler gates are aligned with said fence and the bit of the other gage key having a height equal to A 38 said spacing between said inner surface and said near edge of said tumbler when the tumbler gates are aligned with said fence;

c. means for adjusting the depth of each of said bits in said keyway to the plane of each tumbler and temporarily fixing said bit at each such depth; and

d. a trio of shims slidably received in said second slot for inserting in said keyway behind said stem to increase the height of said bit, each shim having a height equal to B.

5. A decoder according to claim 4 wherein:

e. A is approximately 0.140 inch;

f. B is approximately 0.040 inch; and

g. said spacing between said inner surface and said near edge of said tumbler when the tumbler gates are aligned with said fence is approximately 0.120 inch.

6. A decoder according to claim 4 wherein said means for adjusting the depth of each of said bits in said keyway includes:

e. A set of spaced notches formed in each gage key, the number of notches being equal to the number of tumblers in said column and the spacing between said notches being the same as the spacing between said tumblers;

f. a gage key dog pivotally supported in said body above said first slot for engaging said notches to fix the position of said gage key in said first slot; and

g. an elongated member slidably received in said first slot for sliding snugly up against the top of said cylinder when said gage key is inserted into said keyway to a predetermined depth which places it in the plane of one of said tumblers, the identity of which is known; and

h. means for temporarily fixing the positoion of said elongated member in said first slot. 

1. A method for decoding a lever tumbler lock iNcluding a case having an inner surface, a bolt having a fence, said bolt being slidably received in said case, a cylinder having a keyway, a column of lever tumblers pivotally supported within said case about a fixed axis intermediate said cylinder and said inner surface, each tumbler having a gate formed therein, the spacings between said inner surface and the near edge thereto of each tumbler when said tumbler gates are aligned with said fence being predetermined and equal and the possible depth settings of said tumblers being predetermined and equidistantly spaced, said method comprising: a. determining by trial and error the key bit height which will pivot said near edge of each tumbler flush against said inner surface by inserting keys each having a single bit into the keyway at each tumbler position and turning said keys therein, the bit of each key being of different height equal to the sum of said spacing between said inner surface and the near edge thereto of the tumbler and one of the possible depth settings; and b. calculating the depth setting for each tumbler by subtracting said spacing between said inner surface and the near edge thereto of the tumbler from the key bit height determined in (a).
 2. A method for decoding a lever tumbler lock including a case having an inner surface, a bolt slidably received in said case, said bolt having a fence, a cylinder including a keyway and a bolt retracting means and being supported within said case for partial rotation about a fixed axis, a column of lever tumblers pivotally supported within said case about a second fixed axis intermediate said cylinder and said inner surface, each tumbler having a gate formed therein, the spacings between said inner surface and the near edge thereto of each tumbler when the gates of the tumblers are aligned with the fence being predetermined and equal, and the possible depth settings of said tumblers being: A + nB wherein A is known and is the shortest possible depth setting, n is 0 or a positive integer and B is a predetermined, constant distance, said method comprising: a. determining the maximum degree of rotation of said cylinder without actuating said bolt retracting means to retract said bolt; b. inserting a gage key having a bit with a height equal to A + said spacing between said inner surface and the near edge thereto of each tumbler when the gates of the tumblers are aligned with the fence into said key way at each tumbler position; c. at each tumbler position sequentially increasing the height of said bit by B and turning said gage key in the keyway to engage the tumbler at such position for pivoting thereof at each height in the sequence until a height is reached at which said cylinder will not make said maximum degree of rotation because said near edge of the tumbler has been pivoted against said inner surface, thereby establishing the immediately preceding bit height in the sequence as the bit height at which the bit pivots said near edge of the tumbler flush against said inner surface; and d. calculating A + nB for each tumbler by subtracting from said immediately preceding bit height said spacing between said inner surface and the near edge thereto of each tumbler when the gages of the tumblers are aligned with the fence.
 3. The method according to claim 2 in which: e. A is approximately 0.140 inch; f. n is an integer in the range of 0 and 6, inclusive; and g. B is approximately 0.040 inch.
 4. A decoder for decoding a lever tumbler lock, said lock including a case having an inner surface, a bolt slidably received in said case, said bolt having a fence, a cylinder including a keyway, and being supported within said case for partial rotation about a fixed axis, a column of lever tumblers pivotally supported within said case about a second fixed axis intermediate said cylinder anD said inner surface, each tumbler having a gate formed therein, the spacing between said inner surface and the near edge thereto of each tumbler when the gates of the tumblers are aligned with the fence being predetermined and equal, and the possible depth settings of said tumblers being: A + nB wherein A is known and is the shortest possible depth setting, n is an integer in the range of 0 and 6 inclusive and B is a predetermined, constant distance, said decoder comprising: a. a body having a first slot and a second slot; b. a pair of interchangeable gage keys slidably and removably received in said first slot for inserting one at a time in said keyway, each of said gage keys including an elongated stem and a bit extending from said stem, the bit of one of said gage keys having a height equal to A + said spacing between said inner surface and said near edge of said tumbler when the tumbler gates are aligned with said fence and the bit of the other gage key having a height equal to A + 3B + said spacing between said inner surface and said near edge of said tumbler when the tumbler gates are aligned with said fence; c. means for adjusting the depth of each of said bits in said keyway to the plane of each tumbler and temporarily fixing said bit at each such depth; and d. a trio of shims slidably received in said second slot for inserting in said keyway behind said stem to increase the height of said bit, each shim having a height equal to B.
 5. A decoder according to claim 4 wherein: e. A is approximately 0.140 inch; f. B is approximately 0.040 inch; and g. said spacing between said inner surface and said near edge of said tumbler when the tumbler gates are aligned with said fence is approximately 0.120 inch.
 6. A decoder according to claim 4 wherein said means for adjusting the depth of each of said bits in said keyway includes: e. A set of spaced notches formed in each gage key, the number of notches being equal to the number of tumblers in said column and the spacing between said notches being the same as the spacing between said tumblers; f. a gage key dog pivotally supported in said body above said first slot for engaging said notches to fix the position of said gage key in said first slot; and g. an elongated member slidably received in said first slot for sliding snugly up against the top of said cylinder when said gage key is inserted into said keyway to a predetermined depth which places it in the plane of one of said tumblers, the identity of which is known; and h. means for temporarily fixing the position of said elongated member in said first slot. 